Never seen blue in mine, but red/orange bands on their arms and antaenna(sp) are common.
I had no problems either until one day there was a problem. Just wait, you'll see.I keep mine with cherries and there are no problems whatsoever, so your mileage may vary. Ghost shrimp aren't biofilm eaters in the way that cherry shrimp are though, so my habit of keeping them well fed might be part of that. It's kind of funny that when a ghost shrimp dies the cherries swarm the corpse, and when a cherry shrimp dies the ghost shrimp swarm the corpse, but neither seems to have much interest in their own kind.
The blue likely came from something you fed them though; I've been trying to breed them for color for a while now with some success, but I've not seen anything other than black/brown, red, and creamy white. A mutation is always possible, but it's not particularly likely.
They've been together for a couple of years now. I realize that that doesn't mean much, and it's entirely possible that they've been up to all sorts of shenanigans when I'm not watching, but the babies crawl all over the ghost shrimp and the ghost shrimp crawl all over the cherries and everyone's happy.I had no problems either until one day there was a problem. Just wait, you'll see.